Electrical control arrangement for a sandblasting machine



July 9, 1968 F. s. DYE, JR 3,391,494

ELECTRICAL CONTROL ARRANGEMENT FOR A SANDBLASTING MACHINE Filed June 21,1967 2 Sheets-Sheet l Z6 ATTORNEYS July 9, 1968 F. S. DYE, JR

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ATTORNEYS United States Patent 3,391,494 ELECTRICAL CONTROL ARRANGEMENTFOR A SANDBLASTING MACHINE Floyd S. Dye, Jr., Rte. 1, Elberton, Ga.30635 Continuation-impart of application Ser. No. 558,206, June 13,1966. This application June 21, 1967, Ser. No. 647,804

Claims. (Cl. 518) ABSTRACT OF THE DISCLOSURE Apparatus for electricallycontrolling the position of the nozzle of a sandblasting machine. Thecontrol is operated either manually or automatically. A first reversiblemotor is utilized to cause horizontal movement of the nozzle and asecond reversible motor moves the nozzle vertically. Rotation of themotors is dictated either directly from an electrical control panel orautomatically by limit switches responsive to nozzle location. A cappingdevice is provided to cover the nozzle tip in the absence of electricalpower to the control arrangement thereby protecting the workpiece fromdamage by excess sandblast.

This application is a continuation-in-part of application Ser. No.558,206, filed on June 13, 1966.

The present invention relates to an electrical arrangement forcontrolling the position of a nozzle of a sandblasting machine tothereby permit precise direction of the sandblast onto the workpiece.

In the past efforts have been made to provide automatic control forsandblasting machines. One such arrangement has taken the form disclosedin Patent 2,953,- 876, issued on Sept. 27, 1960. This structure utilizescompressed air to control nozzle movement in the horizontal direction.The employment of a suitable piston and cylinder arrangement to effectnozzle movement by compressed air greatly increases space required forsuch a machine. This can be appreciated by reference to the patentwherein it becomes apparent that to move the nozzle to the righthandside of the machine, the piston rod and the nozzle carriage actuatormust extend beyond the machine by a distance nearly half the width ofthe machine. It can also be seen from the patent that use of thecumbersome piston cylinder restricts the nozzle in traversing the fullwidth of the machine. A further deficiency of such known equipment isthe irregularity of the air supply to the nozzle moving cylinder. Thiscauses uneven travel of the nozzle and contributes to a poordistribution of the sandblast on the workpiece.

It is therefore a principal object of the invention to provide a compactelectrical control arrangement for a sandblasting machine which requiresa minimum of space. Such an arrangement permits a number of machines tobe positioned closely to one another so that a single operator canmonitor the simultaneous operation of several sandblasters.

Another object is to provide a control arrangement which permits thenozzle to travel the full width and height of the sandblasting machine.

An additional object of the electrical nozzle control arrangement is tomove the nozzle at a smooth constant rate thereby improving the eflectof the sandblast on the workpiece.

A still further object of the invention is to provide a safety cappingdevice to interrupt the sandblast to the workpiece should the powersupply to the electrical means controlling the nozzle movement beinterrupted.

The foregoing objects are accomplished by providing first and secondreversible electric motors to drive the nozzle in the horizontal andvertical directions respectively. The motors may be controlled directlyby actuation of suitable pushbuttons electrically connected to themotors, or they may be under the automatic control of a preselectedprogram determined by limit switches which are actuated in response tonozzle location. A normally energized electrical device is associatedwith a nozzle capping arrangement whereby on interruption of powersupply to the control system, the device is de-energized so as torelease a cap which prevents the sandblast exiting from the nozzle fromreaching the workpiece.

The entire scope of the invention will become more fully apparent whenconsidered in light of the following detailed description of anillustrative embodiment of the invention and from the appended claims.

The illustrative embodiment may be best understood by reference to theaccompanying drawings, wherein:

FIGURE 1 is a view in perspective of a sandblasting machineincorporating the electrical control arrangement of the invention;

FIGURE 2 is a fragmented view in perspective of the nozzle cappingarrangement located on the opposite side of the sandblasting machinefrom that observable in FIG- URE 1;

FIGURE 3 is a fragmented, enlarged view of the movement limitingarrangement for the nozzle, the control panel 102 of FIGURE 1 beingomitted for convenience of illustration; and

FIGURE 4 is a block diagram illustrating one form which the electricalcontrol circuitry may take.

Referring now to the drawings, the structure of the sandblaster willfirst be described in detail. In FIGURE 1 there is illustrated aconventional sandblasting machine curtain generally indicated at 10.This curtain comprises a main frame 12 for supporting two spaced,flexible curtain portions 14 and 16. The bottom edge of curtain portion14 and the top edge of curtain portion 16 are joined by a plate member18. A pair of spaced horizontally extending rail members 20 and 22 aresuitably attached to plate 18. A carriage assembly 24 having groovedwheels 25 is supported between rails 20 and 22. The wheels permit thecarriage to be moved along the rails in a horizontal path. Plate 18 isprovided with a horizontally extending slot (not shown) which is coveredwith a flexible sealing element 26 having a slit 28 along the lengththereof. A sandblast nozzle 30 is firmly supported by carriage 24 andprojects through the slit 28. A flexible hose 32 serves to carry sandunder high pressure from a compression source to nozzle 30.

FIGURE 2 illustrates the details of the nozzle portion which projectsthrough the slit in flexible sealing element 26. A deflection plate 34is attached to the nozzle in closely spaced relationship with respect toelement 26. Plate 34 and element 26 insure that sand exiting from nozzletip 36 cannot be deflected back through the opening in plate 18 throughwhich the nozzle projects.

A safety capping arrangement is also associated with the portion ofnozzle 30 shown in FIGURE 2. More particularly, arms 38 and 40,interconnected at one of their ends by a cap element 42, are pivotallyconnected to nozzle 30 at their other ends, as indicated at 44. Cap 42is normally held out of the path of sand exiting from nozzle tip 36 by aforce exerted on wire 46 connected intermediate the ends of arm 38 andpassing through the deflection plate 34 and slit 28 to the opposite sideof the sandblast curtain 10. When this force is released, as for examplein the case of power failure, which also terminates movement of thenozzle, the cap arrangement pivots about 44 to the position shown indash lines to thereby interpose cap 42 between the nozzle tip 36 and theworkpiece. The workpiece is thereby prevented from damage which wouldotherwise be caused by an excess flow of sand against a localizedportion of the workpiece.

Now that structure of the sandblasting a paratus has been described,attention will be directed to the control mechanisms for positioning thesandblasting nozzle 30. In this regard, reference will be made toFIGURES l and 3. A reversible drive motor 48 is fixed to the lowerhorizontal rail 22 at one end thereof. A driving element in the form ofa sprocket (not shown) is appropriately connected to the drive shaft ofmotor 48. An additional sprocket (FIGURE 3) which serves as a rotatableguide element is supported between rails 20 and 22 at the opposite endof rail 22 from that to which motor 48 is mounted. A flexible length ofchain 52 is joined at one of its ends to one side of carriage 24. Thischain passes over the sprocket associated with motor 48, past carriage24, around sprocket 50, and back to carriage 24 where its other end isconnected to the side of the carriage opposite that to which the firstchain end is connected. From the foregoing description it is apparentthat as motor 48 is driven in forward or reverse directions, thecarriage 24 is moved horizontally along rails 20 and 22.

In addition to horizontal movement, the carriage 24 also may betranslated vertically. This is accomplished by journalling ahorizontally extending shaft 54 in support elements 56 mounted at thetop, and at opposite sides, of main frame 12. Shaft 54 is connected tothe upper rail 20 of the carriage supporting arrangement by means ofcables 58 positioned close to the ends of shaft 56. A gear 60 mounted atone end of shaft 56 is suitably interconnected with the drive shaft of areversible motor 62 fixed to frame 12. As this motor is operated, shaft54 is rotated to either wind cables 58 thereabout to raise thenozzle-supporting carriage 24, or to unwind the cables thereby loweringthe carriage.

It should be understood that curtain portion 14 is preferably suppliedfrom a roll fixed to frame 12 near the top so that as carriage 24 islowered, curtain material is unrolled, whereas when carriage 24 israised, curtain material is wrapped on the roll. Curtain portion 16 issimilarly supplied from a roll fixed to frame 12 near its bottom.

The invention provides, as is most clearly illustrated in FIGURE 3,means for controlling the limits of travel of the nozzle-supportingcarriage 24 in the horizontal and vertical directions. With respect tothe former, this is accomplished by extending the shaft 64, whichcarries sprocket 50, to a gear reduction box 66. The output shaft 68from box 66 is connected to a disk 70 to rotate same. Since the rotationof sprocket 50 is dependent on that of motor 48, the appropriateselection of gears in box 66 results in disk 70 rotating in proportionto the horizontal travel of the carriage 24. This fact is utilized byselectively attaching projecting cam elements 72 to the circumferentialedge of disk 70. The selective positioning of elements 72 is performedby the operator who manually moves the carriage horizontally to thedesired limits of travel for the particular workpiece to be operatedupon and sets the cam elements in positions which, during automaticoperation, will permit the carriage to move horizontally only withinthese limits. A limit switch 74, attached to rail 20, is placed in thepath of these cam elements. Thus, during automatic operation of theequipment, each time a cam element 72 engages limit switch 74, motor 48reverses to cause the nozzle to change its direction of movement. Thisoperation will be described in detail hereinafter.

To control the limits of vertical movement of the nozzle, a verticallyextending bar 76 is mounted on frame 12. A pair of cams 78 and 80 areselectively positioned in spaced relationship along bar 76. These camsare located in the path of a limit switch 82. In a fashion similar tothat described with respect to switch 74, the actuation of switch 82results in the reversal of motor 62 to change the direction of verticalmovement of the nozzle.

Now that the mechanical structure of the invention has been discussed,an electrical system for implementing either manually or automaticallycontrolled movement of the nozzle will be described. In this regard, arepresentative circuit is illustrated in FIGURE 4. The circuitschematically illustrates identical arrangement for controlling each ofthe reversible motors 48 and 62. For purposes of description, the systemfor motor 48 will be detailed. The motor 48 is connected to a motorreversing means which in practice may take many forms. For example, amagnetic switch could be employed, the actuation of which changes thesense of energization of the reversible motors field thereby reversingits operation. The motor reversing means is controlled by the selectiveactuation of a manual left switch 84, a manual right switch 86 and anautomatic horizontal movement switch 88. These switches are illustratedin FIGURE 1 as being of the conventional pushbutton type. Switches 84and 86 each comprise a ganged contact pair arranged such that theclosing of one contact of each pair results in the opening of the othercontact. Since each contact is in a separate energizing path to themotor reversing means, such an arrangement insures that only one path tothe reversing means can be completed. Switch 88 when actuated permitsthe operation of limit switch 74 to effect the motor reversing means.

The illustrated positions of switches 84, 86 and 88 are those whichexist when the system is at rest. When it is desired to manually movethe nozzle to the left, switch 84 is actuated to complete a firstcurrent path to the motor reversing means. For movement to the right,the same procedure would be followed except that switch 86 would beoperated. If automatic operation is desired, switch 88 is closed. Sincelimit switch 74 is in the position shown, initial automatic movement ofthe carriagesupported nozzle is to the left. This movement continuesuntil the cam element 72 limiting travel to the left engages switch 74to reverse its position. When this occurs, the carriage begins itstravel to the right and so continues until the other cam element 72returns the limit switch to the illustrated position.

Of course, the operation of the vertical movement control means is thesame as that for horizontal movement. The manual up and manual downswitches are designated as 90 and 92, respectively, and the automaticvertical movement switch is labelled as 94, in FIGURES l and 4.

The control device for the capping arrangement is illustrated in FIGURESl, 2 and 4. More specifically, a solenoid is connected to the electricalpower supply for the system. This solenoid is mounted on carriage 24 andis designated as 96. The armature of solenoid 96 is connected to wire 46which is most clearly shown in FIGURE 2. A flexible electricalconnection 98 from solenoid 96 is passed over pulley 100 to the powersupply. So long as the power supply to the control system isuninterrupted, solenoid 96 is energized, and the capping device is heldin the position shown in the full lines of FIGURE 2. When the powersupply is interrupted, the solenoid armature is released therebypermitting the cap 42 to cover the nozzle tip 36 thereby preventing sandexiting from the nozzle from reaching the workpiece towards which thenozzle is directed.

For the purposes of clarity, FIGURE 1 does not illustrate the electricalconnections between the various components. However, it should beappreciated that switches 84, 86, 88, 90, 92 and 94 are connected fromthe control panel 102, attached to frame 12, to box 104 located at thetop of the sandblasting machine. Box 104 contains the motor reversingmeans for the motors 48 and 62, as well as the connections from thecontrol arrangement to the power supply. Of course, each reversing meansis also electrically connected from box 104 to its respective motor.

From the foregoing description it is apparent that the present inventionprovides an electrical control for a sandblasting machine which permitsthe nozzle to be moved independently or simultaneously in the verticaland horizontal directions either under manual control or automatically.Due to the compactness of the equipment required for electrical control,the travel of the nozzlesupporting carriage 24 extends oversubstantially the full width and height of the machine, withoutrequiring structure which extends significantly beyond the machine. Thesafety capping arrangement insures that the workpiece will not bedamaged in the event of power supply interruption to the electricalcontrol system.

The above-described embodiment is illustrative of a preferred embodimentof the invention but is not intended to limit the possibilities ofinsuring the features of full nozzle travel at constant speed. Forexample, many other arrangements for the limit switches are possible. Itshould also be appreciated that although the invention described hereinis particularly adaptable to lettering or otherwise carving on stone, itis applicable to other environments in which comminuted abrasivematerials are directed under high pressure towards a work surface foreroding or cleaning same. The structure disclosed herein is an exampleof an arrangement in which the inventive features of this disclosure maybe utilized, and it will become apparent to one skilled in the art thatcertain modifications may be made within the spirit of the invention asdefined by the appended claims.

What is claimed is:

1. A machine for directing comminuted abrasive material towards aworkpiece, comprising: a nozzle through which said material is passed; acarriage supporting said nozzle; a first reversible electric motoroperatively connected to said carriage for moving same in a horizontaldirection; a second reversible electric motor operatively connected tosaid carriage for moving same in a vertical direction; a limit switchoperatively connected to each of said reversible motors; adjustable cammeans for selectively actuating said limit switches in response tocarriage movement to reverse the motor associated with an actuatedswitch; manually operable switches selectively operatively connected tosaid reversible motors to control said motors independently of the limitswitches; a capping arrangement positioned in proximity to said nozzle;and means responsive to the interruption of a power supply to saidmachine for interposing said capping arrangement between the nozzle andsaid workpiece.

2. A machine for directing comminuted abrasive material towards aworkpiece, comprising: a nozzle through which said material is passed; acarriage supporting said nozzle; a first reversible electric motormounted at one side of said machine to drive a first sprocket; a secondsprocket attached to the opposite side of said machine; a length ofchain connected at opposite sides of said carriage and passing over saidfirst and second sprockets whereby rotation of the first motor causesthe carriage to move in a horizontal direction; a second reversibleelectric motor operatively connected to said carriage for moving same ina vertical direction; a limit switch operatively connected to each ofsaid reversible motors; a plurality of adjustable cam means forselectively actuating said limit switches in response to carriagemovement to reverse the motor associated with an actuated switch; a gearreduction box operatively connected to one of said sprockets; a diskconnected to the gear reduction box to be rotatably driven thereby; atleast two of said adjustable cam means being mounted on the disk toengage one of the limit switches as the disk is rotated; and manuallyoperable switches selectively operatively connected to the reversiblemotors to control said motors independently of the limit switches.

3. A machine as set forth in claim 1, wherein said capping arrangementis pivotally connected to the nozzle and said means responsive to powersupply interruption includes a solenoid normally energized by the powersupply and means connecting the capping arrangement to said solenoid toretain the capping arrangement out of the path between the nozzle andthe workpiece when the solenoid is energized.

4. A machine as set forth in claim 2, further comprising: a cappingarrangement positioned in proximity to said nozzle; and means responsiveto the interruption of a power supply to said machine for interposingsaid capping arrangement between the nozzle and said workpiece.

5. A machine as set forth in claim 4, wherein said capping arrangementis pivotally connected to the nozzle and said means responsive to powersupply interruption includes a solenoid normally energized by the powersupply and means connecting the capping arrangement to said solenoid toretain the capping arrangement out of the path between the nozzle andthe workpiece when the solenoid is energized.

References Cited UNITED STATES PATENTS 1,882,541 10/1932 Billman 51-82,495,269 l/l950 Lindmark 51-15 2,611,219 9/1952 Gladfelter 51--82,953,876 9/1960 Zieber et al 51-8 3,283,450 11/1966 Greenberg et al5l14X LESTER M. SWINGLE, Primary Examiner.

